Sniper Elite 3 has 110 Collectible Locations which include 60 War Diaries, 20 Collectible Cards, 22 Sniper Nests and 8 Long Shots. You will gain 100% completion when you finish all 8 campaign missions. If you manage to find all of these you can earn these five trophies / achievements.
Silver
Archivist (20G)
The gathering (20G)
Nesting instinct (20G)
A shot in the dark (40G)
Bronze
Casual Reader (10G)
Mission 1
Mission 2
Mission 3
Mission 4
Mission 5
Mission 6
Mission 7
Mission 8